Device for extraction of pins at fixation means for fixation of bone fragments at bone fractures

ABSTRACT

The present invention relates to a device for extraction of pins at fixation means for fixation of bone fragments at bone fractures. The fixation means ( 2 ) includes a sleeve ( 6 ) and at least one pin ( 7 ) provided in said sleeve. The sleeve ( 6 ) has at a front end portion ( 9 ) at least one opening ( 10 ) in a longitudinal side thereof. A front part ( 11 ) of the pin ( 7 ) extends, when it is located in an operating position, out of the sleeve ( 6 ) through the opening ( 10 ) and engage bone material of one of the bone fragments ( 3, 4 ). The extraction device ( 1 ) is adapted to pull the pin ( 7 ) in a backwards direction relative to the sleeve ( 6 ) in order to withdraw the front part ( 11 ) of the pin ( 7 ) from bone material of one of the bone fragments ( 3, 4 ) and into the sleeve ( 6 ). The extraction device ( 1 ) comprises means ( 12, 13 , and  14 ) which are provided to draw or pull the pin ( 7 ) backwards relative to the sleeve ( 6 ) without thereby subjecting the pin ( 7 ) to torsional forces in relation thereto.

The present invention relates to a device for extraction of pins at fixation means for fixation of bone fragments at bone fractures. The fixation means includes a sleeve and at least one pin provided in said sleeve. The sleeve has at a front end portion at least one opening in a longitudinal side thereof. A front part of the pin extends, when it is located in an operating position, out of the sleeve through the opening and engage bone material of one of the bone fragments. The extraction device is adapted to pull the pin in a backwards direction relative to the sleeve in order to withdraw the front part of the pin from bone material of one of the bone fragments and into the sleeve. The invention also relates to use of the abovementioned device.

Extraction devices of the type defined above are described in U.S. Pat. No. 4,498,468. At this prior art extraction device, an extraction handle subjects the pin to torsional forces when said pin is pulled backwards into the sleeve thereby by turning or rotating the extraction handle. These torsional forces press the front part of the pin against one edge of the opening in the sleeve from which said front part of the pin extends out of the sleeve. The front part of the pin is pressed against one edge of the opening during the entire drawing-in movement and until the front part of the pin is situated within the opening. It has been noticed that the front part of the pin is pressed against the edge of the opening with such power that the front part cuts into the edge or vice versa such that said front part clings to said edge. This means that there is a risk that the front part of the pin is broken or that the pin breaks at a threaded rear part since this part is weakened because of the threads. If the front part of the pin is broken, this part remains in the bone and if the pin is broken at the threaded rear part thereof, said pin can not be withdrawn or the withdrawal or extraction will at least cause some problems. These drawbacks are unacceptable when after fixation of the bone fragments, the fixation means shall be removed.

The object of the present invention is to eliminate this problem and this is arrived at by providing the device defined above with the characterizing features of primarily subsequent claim 1.

Said characterizing features see to that the front part of the pin is not pressed against the edge of the opening in the sleeve when said pin is withdrawn or extracted into the sleeve through the opening and thus, the front part can not cling to the edges of the opening. This means that the risk of breaking the pin at the front or at the back is eliminated.

The invention will be further described below with references to the accompanying drawings, in which

FIG. 1 is a perspective view of a device according to the invention, wherein the device is connected to a fixation means for pulling the pin thereof backwards;

FIG. 2 is a side view of the device of FIG. 1;

FIG. 3 is a perspective view of an inner extraction member forming part of the device of FIG. 1;

FIG. 4 is a longitudinal section of the inner extraction member of FIG. 3;

FIG. 5 is a perspective view of an outer extraction member forming part of the device of FIG. 1;

FIG. 6 is a side view of the outer extraction member of FIG. 5; and

FIG. 7 is a side view of an extraction handle forming part of the device of FIG. 1.

The extraction device 1 illustrated in the drawings is adapted for extraction or withdrawal of fixation means 2 for fixation of bone fragments 3, 4 at bone fractures 5. The bone fragments 3, 4 to be fixed can be bone fragments at femoral fractures, collar bone fractures or at fractures of any other bone in the body.

The fixation means 2 may be of any prior art type see e.g. U.S. Pat. No. 4,498,468—and it may include a sleeve 6 and at least one pin 7 provided in said sleeve 6. The sleeve 6 has an open rear end portion 8 and a front end portion 9 having at leant one opening 10 in a longitudinal side of the sleeve 6 but being otherwise closed. The pin 7 can be driven into the sleeve 6 in a forward direction by means of a drawing-in instrument (already known per se and therefore not shown) such that a front part 11 of the pin 7 is brought to protrude through the opening 10 until it engages the bone material of the surrounding bone fragment 4. Hereby, the fixation means 2 fix the bone fragments 3, 4 at each other.

The extraction device 1 is adapted for withdrawal of the front part 11 of the pin 7 from the bone material of the bone fragment 4 for being able to remove the sleeve 6 when the fracture 5 is healed. To accomplish this, the extraction device 1 comprises, in the embodiment shown, three members, namely an inner extraction member 12, an outer extraction member 13 and a manully operable extraction handle 14, and these three members are provided to pull the pin 7 backwards relative to the sleeve 6 without thereby subjecting the pin 7 to torsional forces in relation thereto. Hereby, one avoids the problem that the front part 11 of the pin 7 engages one of the edges of the opening 10 when said pin is pulled into the opening 10 and this results in that said front part 11 of the pin 7 can not cut into said edge or vice versa such that the front part 11 clings to said edge.

In the embodiment shown, the inner extraction member 12 consists of an elongated rod which at a front end portion 15 has an axially directed hole with inner threads 16. The front end portion 15 has such a diameter that it can be pushed into the rear end portion 8 of the sleeve 6 and its inner threads 16 mesh with outer threads 17 on a rear part 18 of the pin 7 such that the inner extraction member 12 can be screwed onto said rear part 18.

The front end portion 15 of the inner extraction member 12 transforms through an edge 19 into such portions 20 of the inner extraction member 12 which preferably have a larger diameter than the front end portion 15. The edge 19 of the inner extraction member 12 may engage a rear edge 21 of the sleeve 6 when the inner extraction member 12 is operating.

The hole with the inner threads 16 in the front end portion 15 of the inner extraction member 12 has preferably an inlet 22 without threads and tapering conically in a direction inwards into the hole. Hereby, the pin 7 can guide the inner extraction member 12 such that the inner threads 16 thereof easily “find” the outer threads 17 of the pin 7, whereby said inner and outer threads 16, 17 more easily mesh with each other in a correct manner when the inner extraction member 12 is screwed onto the pin 7. In combination with the inlet 22 without threads in the hole of the inner extraction member 12 or as an alternative thereto, an outer portion of the rear part 18 of the pin 7 may also be without threads and have a conically increasing diameter in a direction towards the outer threads 17 of the rear part 18.

The inner extraction member 12 has a hole with inner threads 23 in a rear end portion 24 and the extraction handle 14 has a front end portion 25 with outer threads 26 which fit or mesh with said inner threads 23. Said front end portion 25 ends at a transverse edge 27 and the extraction handle 14 has at the back a transverse handle member 28 which is engaged in order to turn or rotate the extraction handle 14.

The rear end portion 24 of the inner extraction member 12 has a rotary preventing member 29, e.g. at least an oval member 29, which can be defined by one or more flat face milled parts of the rear end portion 24 which for the rest has a circular cross section. The purpose of the rotary preventing member 29 will be described hereinafter.

The outer extraction member 13 consists of, in the illustrated embodiment, an elongated sleeve which is open at a front end portion 30 as well as at a rear end portion 31. This sleeve is sized such that the inner extraction member 12 can be inserted thereinto and displaced in an axial extraction direction R relative to said sleeve. The rear end portion 31 of the outer extraction member 13 has inside the sleeve a rotary preventing member 32, e.g. in the form of a flat constriction of the interior of the sleeve, the rest of which has a circular cross-sectional shape.

The inner extraction member 12 can be inserted into the outer extraction member 13 so far that rotary preventing members 29 of the former cooperate with the rotary preventing members 32 of the latter in such a way that they prevent rotation of the inner extraction member 12 and the pin 7 relative to the outer extraction member 13 and the sleeve 6 about a geometric centre line C which extends along the inner and outer extraction members 12, 13 and the sleeve 6 and the pin 7 when said inner extraction member 12 and said pin 7 are pulled backwards in the direction of extraction or withdrawal R.

The outer extraction member 13 has a through hole 33 with preferably the same diameter along its entire length except for said rotary preventing member 32.

The outer extraction member 13 is held fast with the hand so that it can not rotate about the centre line C and in order to facilitate this holding it may have a sideways or laterally directed handle 34 or similar, which preferably can be provided at the rear end portion 31 of the outer extraction member 13.

The lengths of the inner and outer extraction members 12, 13 and the location as well as the shape of the rotary preventing members 29, 32 are preferably chosen such that the extraction handle 14 can cooperate with the inner extraction member 12 only when said inner extraction member 12 is inserted into the outer extraction member 13 such that the rotary preventing members 29, 32 of said extraction members 12, 13 cooperate with each other.

The outer threads 26 of the extraction handle 14 have such length and/or the inner threads 23 in the rear end portion 24 of the outer extraction member 13 have such length that the extraction handle 14 can be screwed together with the inner extraction member 12 so far, but not farther, that the pin 7 is drawn or pulled backwards so far, but not farther than that the tip 35 of the pin 7 is situated within the opening 10 in the sleeve 6. This means that the tip 35 of the pin 7 can cooperate with a rear edge of the opening 10 and thereby pull the sleeve 6 backwards together therewith when said sleeve shall be withdrawn from the bone fragments 3, 4 by means of the extraction handle 14 and the extraction force of the extraction handle 14 is transferred to the pin 7 through the inner extraction member 12.

The inner extraction member 12 may have lateral holes 36, 37 which extend into the holes with the inner threads 16, 23 such that said holes can be flushed clean at the lateral holes 36, 37.

The device described above can be operated as follows:

-   -   1) the inner extraction member 12 is screwed onto the pin 7 by         right hand rotation,     -   2) the outer extraction member 13 is threaded onto the inner         extraction member 12 and located such that the rotary preventing         members 29, 32 of said extraction members 12, 13 cooperate with         each other,     -   3) the extraction handle 14 is moved, through the outer         extraction member 13, into the inner extraction member 12 and is         screwed thereonto by right hand rotation,     -   4) the extraction handle 14 is continuously rotated to the right         when the outer extraction member 13 engages the sleeve 6 and         thereby, the extraction handle 14 will draw or pull, through the         inner extraction member 12, the pin 7 backwards relative to the         sleeve 6 in the direction of extraction or withdrawal R.

The device described above is particularly suitable for use at fixation means 2 wherein the sleeve 6 and the pin 7 consists of titanium material, but may of course also be used at fixation means 2 of other materials, e.g. stainless steel.

The invention is not limited to the device described above, but may vary within the scope of the subsequent claims. Thus, the extraction handle 14 may be displaceable backwards relative to the outer extraction member 13 instead of being rotated, the rotary preventing members 29, 32 may be of a totally different type and be located in other ways than shown and described and the lengths of the various members and threads may be chosen differently than described. Instead of choosing certain lengths on the outer threads 26 of the extraction handle 14 and/or the inner threads 23 of the inner extraction member 12 for limiting the length of extraction or withdrawal of the pin 7, other types of members limiting the extraction can be provided. The opening 10 in the sleeve 6 may be round or oval or substantially round or oval and the front part 11 of the pin 7 may have a rounded side by means of which it can cooperate with front parts of the opening 10, and another side, opposite to said side, which is flat or substantially flat and which can cooperate with rear parts of the opening 10. 

1. Device for extraction of pins at fixation means for fixation of bone fragments at bone fractures, wherein the fixation means (2) includes a sleeve (6) and at least one pin (7) provided in said sleeve (6), wherein the sleeve (6) at a front end portion (9) has at least one opening (10) in a longitudinal side thereof, wherein a front part (11) of the pin (7) extends, when said pin (7) is located in an operating position, out of the sleeve (6) through the opening (10) and engage bone material of one of the bone fragments (3, 4), and wherein the extraction device (1) is adapted to pull the pin (7) in a backwards direction relative to the sleeve (6) in order to withdraw the front part (11) of the pin (7) from bone material of one of the bone fragments (3, 4) and into the sleeve (6), characterized in that the extraction device (1) comprises an inner extraction member (12) which is connectable to the pin (7), an outer extraction member (13) which is connectable to the sleeve (6) and in which the inner extraction member (12) is insertable and an extraction handle (14) which is rotatable relative to the outer and inner extraction members (13, 12) in order to extract the pin (7) in a direction (R) of extraction or withdrawal relative to the outer extraction member (13) and the sleeve (6), that the outer extraction member (13) is manually holdable in order to prevent that the outer extraction member (13) could rotate when the extraction handle (14) is rotated, and that the outer and inner extraction members (13, 12) are constructed such that the outer extraction member (13) prevents that the inner extraction member (12) could rotate relative to the outer extraction member (13) when the extraction handle (14) is rotated.
 2. Device according to claim 1, characterized in that the outer and inner extraction members (13, 12) are provided with rotary preventing members (32, 29), which could cooperate with each other in order to prevent that the inner extraction member (12) could rotate relative to the outer extraction member (13), that the rotary preventing members (32) of the outer extraction member (13) are non-circular parts of a through hole (33) in the outer extraction member (13), and that the rotary preventing members (29) of the inner extraction member (12) are non-circular parts.
 3. Device according to claim 2, characterized in that the rotary preventing members (32) of the outer extraction member (13) are provided in a rear end portion (31) of the outer extraction member (13), and that the rotary preventing members (29) of the inner extraction member (12) are provided on a rear end portion 24 of the inner extraction member (12).
 4. Device according to claim 3, characterized in that the lengths of the inner and outer extraction members (12, 13) and the location and shape of their rotary preventing members (29, 32) are chosen such that the extraction handle (14) can cooperate with the inner extraction member (12) only in order to draw or pull said inner extraction member (12) backwards in the direction of extraction or withdrawal (R) only when said inner extraction member (12) is inserted into the outer extraction member (13) such that their rotary preventing members (29, 32) cooperate with each other.
 5. Device according to claim 1, characterized in that at least one part (26 and/or 23) limiting the extraction or withdrawal is provided in order to ensure that the extraction handle (14), through the inner extraction member (12), can draw or pull the pin (7) backwards so far relative to the sleeve (6), but not farther, that a tip (35) of the pin (7) is situated in the opening (10) of the sleeve (6), and can thereby cooperate with a rear edge of the opening (10) such that the pin (7), through said cooperation with the rear edge of the opening (10), can draw or pull the sleeve (6) backwards along with it in the direction of extraction or withdrawal (R) when the sleeve (6) shall be pulled out of the bone fragment (3, 4) by means of the extraction handle (14).
 6. Device according to claim 5, characterized in that said extraction limiting part (26 and/or 23) consists of that the extraction handle (14) has outer threads (26) with such length and/or that the inner extraction member (12) has inner threads (23) with such length that the length of screwing together of the outer threads (26) of the extraction handle (14) and the inner threads (23) of the inner extraction member (12) is limited.
 7. Device according to claim 1, characterized in that a rear part (18) of the pin (7) has outer threads (17), that a front end portion (15) of the inner extraction member (12) has a hole with inner threads (16) which mesh with the outer threads (17) of the pin (7), and that the hole of the inner extraction member (12) has an inlet (22) without threads, said inlet (22) tapering conically in a direction inwards into the hole, and/or that the rear part (18) of the pin (7) has an outer portion without threads, said outer portion having a conically increasing diameter in a direction towards the outer threads (17) of the rear part (18).
 8. Device according to claim 1, characterized in that the inner extraction member (12) has front end portion (15) with such outer dimensions or size that it can be inserted into a rear end portion (8) of the sleeve (6).
 9. Device according to claim 8, characterized in that the front end portion (15) of the inner extraction member (12), which can be inserted into a rear end portion (8) of the sleeve (6), transforms into inner portions (20) of the inner extraction member (12) having larger outer dimensions through an edge (19) which can engage a rear edge (21) of the sleeve (6) when the inner extraction member (12) is operating.
 10. Device according to claim 1, characterized in that the inner extraction member (12) is an elongated rod and has a front end portion (15) with a hole which is provided with inner threads (16) which mesh with outer threads (17) on the pin (7), that the inner extraction member (12) has a rear end portion (24) with a hole with inner threads (23) which fit or mesh with outer threads (26) on the extraction handle (14), that the outer extraction member (13) is an elongated sleeve which is open in both ends, and that the inner extraction member (12) fits into the outer extraction member and is axially displaceable in relation thereto.
 11. Device according to claim 10, characterized in that the inner extraction member (12) includes lateral holes (36, 37) which extend into the holes with the inner threads (16, 23) such that said holes can be flushed clean through said lateral holes (36, 37).
 12. Device according to claim 1 characterized in that the outer extraction member (13) has a sideways or laterally directed handle (34) for holding said outer extraction member (13) such that it does not rotate when the pin (7) is drawn or pulled out in the direction of extraction or withdrawal (R).
 13. Device according to claim 1, characterized in that the device consists of only three members, namely an inner extraction member (12), an outer extraction member (13) and an extraction handle (14).
 14. Device according to claim 1, characterized in that the opening (10) in the sleeve (6) is round or oval or substantially round or oval, and that the front part (11) of the pin (7) has a rounded side by means of which it can cooperate with front parts of the opening (10), and another side, opposite to said side, which is flat or substantially flat and which can cooperate with rear parts of the opening (10).
 15. Device according to claim 1, characterized in that the sleeve (6) and pin (7) are made of titanium.
 16. Device according to claim 1, characterized in that the sleeve (6) and pin (7) are made of stainless steel. 